1. Field of the Invention
The present invention relates to a process and apparatus for producing finished wood sheets from rough cut wood and particularly to producing wood panels for use in making multi-layer wood products.
The invention relates to a method and a device for the production of wood sheets from cut wood. Wood sheets in this context are to be understood as relatively thin wood panels which are thicker than 2 to 3 mm and which are processed into high-grade products made up of one or more layers, such as, for example, natural wood panels made up of several layers, glue binders, glued laminated wood, window ledges, solid wood panels and the like.
2. Description of the Prior Art
According to the prior art, such wood sheets are generally produced in that the cut wood is firstly dried to a relatively low degree of humidity and that the cut wood planks are then sawn by means of bandsaws and the like into the individual wood sheets. Such a method has several disadvantages. On the one hand, the quality of the wood sheets produced in this way leaves something to be desired, since the wood sheets in the sawing process easily fray or become ragged, particularly in the region of knots and edges, with this occurring all the more, the drier the cut wood is which is to be cut. This results in a relatively high proportion of damaged goods.
A further disadvantage of the known method is to be seen in the relatively poor yield, i.e. the proportion of waste is relatively high. This lies in the fact that waste occurs on each cut by the saw, corresponding to the thickness of the saw cut. If, for example, wood sheets are produced with a thickness of 4 mm and if the saw cut width is 2.5 mm, then a wastage of approximately 40% of the cut wood material already results from this.
A further disadvantage in the method according to the prior art is to be seen in that in the production of the wood sheets, a relatively large amount of energy is consumed. The reason for this is that owing to the relatively wide cutting slit of the saw cut, a large amount of material has to be machined off.
On the other hand, it is known to produce wood sheets in a cutting device by means of a sawdust-free cutting process such as is described in PCT application No. WO 88/00517 entitled "Process and Device for Cutting Up Tree Trunks into Wood Products Without Shavings", incorporated herein by reference. In the sawdust-free process, a tree trunk or rough cut wood plank is axially guided against a knife which separates a sideboard laterally from the tree trunk. The results which have been able to be achieved hereby to date are, however, likewise not very satisfactory. On the one hand, the yield here is increased by avoiding the saw cut, but on the other hand in this method a so-called residual sheet occurs, i.e. after cutting off the maximum number of wood sheets which an be cut from the cut wood plank with the required nominal thickness, a remainder is left behind, which has a smaller thickness than the nominal thickness of the wood sheets which are to be produced, and is therefore unable to be used further, in any case not in the respective continuation of production.
Furthermore, the quality of the wood sheets thus produced leaves much to be desired, especially since the individual wood sheets leave the cutting device in a greatly warped state, which derives form the fact that the wood sheets cut off from the cut wood plank are carried away obliquely to their original direction of transportation. In the known cutting device, consequently, the problem is posed, which has not been solved to date, of restoring such warped wood sheets into their non-warped, level or flat state at a justifiable expense.
The invention is therefore based on the problem of indicating a method which provides high-grade wood sheets at a justifiable expense, in which at the same time a maximum yield is to be achieved and, moreoever, the necessary expenditure of energy is to be kept as low as possible. Furthermore, a device is to be created, which satisfies the above-mentioned conditions.